Epilepsy occurs in approximately 1% of the population worldwide, (Thurman et al., 2011) of which 70% are able to adequately control their symptoms with the available existing anti-epileptic drugs (AED). However, 30% of this patient group, (Eadie et al., 2012), are unable to obtain seizure freedom from the AED that are available and as such are termed as suffering from “treatment-resistant epilepsy” (TRE).
Treatment-resistant epilepsy was defined in 2009 by the International League Against Epilepsy (ILAE) as “failure of adequate trials of two tolerated and appropriately chosen and used AED schedules (whether as monotherapies or in combination) to achieve sustained seizure freedom” (Kwan et al., 2009).
Individuals who develop epilepsy during the first few years of life are often difficult to treat and as such are often termed treatment-resistant. Children who undergo frequent seizures in childhood are often left with neurological damage which can cause cognitive, behavioral and motor delays.
Childhood epilepsy is a relatively common neurological disorder in children and young adults with a prevalence of approximately 700 per 100,000. This is twice the number of epileptic adults per population.
When a child or young adult presents with a seizure, investigations are normally undertaken in order to investigate the cause. Childhood epilepsy can be caused by many different syndromes and genetic mutations and as such diagnosis for these children may take some time.
One such childhood epilepsy is Dravet syndrome. Onset of Dravet syndrome almost always occurs during the first year of life with clonic and tonic-clonic seizures in previously healthy and developmentally normal infants (Dravet, 2011). Symptoms peak at about five months of age. Other seizures develop between one and four years of age such as prolonged focal dyscognitive seizures and brief absence seizures.
Seizures progress to be frequent and treatment-resistant, meaning that the seizures do not respond well to treatment. They also tend to be prolonged, lasting more than 5 minutes. Prolonged seizures may lead to status epilepticus, which is a seizure that lasts more than 30 minutes, or seizures that occur in clusters, one after another.
Prognosis is poor and approximately 14% of children die during a seizure, because of infection, or suddenly due to uncertain causes, often because of the relentless neurological decline. Patients develop intellectual disability and life-long ongoing seizures. Intellectual impairment varies from severe in 50% patients, to moderate and mild intellectual disability each accounting for 25% of cases.
There are currently no FDA approved treatments specifically indicated for Dravet syndrome. The standard of care usually involves a combination of the following anticonvulsants: clobazam, clonazepam, levetiracetam, topiramate and valproic acid.
Stiripentol is approved in Europe for the treatment of Dravet syndrome in conjunction with clobazam and valproic acid. In the US, stiripentol was granted an Orphan Designation for the treatment of Dravet syndrome in 2008; however, the drug is not FDA approved.
Potent sodium channel blockers used to treat epilepsy actually increase seizure frequency in patients with Dravet Syndrome. The most common are phenytoin, carbamazepine, lamotrigine and rufinamide.
Management may also include a ketogenic diet, and physical and vagus nerve stimulation. In addition to anti-convulsive drugs, many patients with Dravet syndrome are treated with anti-psychotic drugs, stimulants, and drugs to treat insomnia.
Common AED defined by their mechanisms of action are described in the following tables: